This invention relates to displaying text symbols and, more particularly, to the display of text symbols that are associated with audio data reproducible from a recording disc.
There are many applications in which it is desirable to reproduce audio information from a prerecorded disc, such as a compact disc (CD), a mini-disc (MD) or the like, and to display text information, notably text symbols, associated with that audio information. For example, in the home entertainment environment, it is desirable to display the words of a song that has been prerecorded on a disc in order to enable the user to sing that song. This application is known as "karaoke"; and karaoke systems are commercially available wherein the user's voice is mixed with the prerecorded musical accompaniment, resulting in enhanced performance.
In other applications, it is desirable to display text symbols associated with information stored on a CD-ROM, such as stored audio information, stored graphics information, and the like. The text symbols may consist of subtitle information, instructions, summaries, translations into different languages, etc.
Information recorded on compact discs, whether it is audio information recorded on a CD or other information recorded on a CD-ROM, typically is recorded in a pre-established format that is not particularly conducive to the display of text symbols. For example, in the environment of an audio CD, digital audio data is recorded in frames with each frame containing 588 bits of synchronizing, control and audio information. This format is illustrated in FIG. 1, with the beginning of a frame being denoted by sync frame data followed by sync control data followed by multiplexed left-channel and right-channel data. The left-channel data includes two 8-bit bytes which form a sample, with three left-channel and three right-channel samples being multiplexed in the first half of the frame; and three left-channel and three right-channel samples being multiplexed in the second half of the frame. An error correcting code, such as CIRC is used to error-correct the six multiplexed samples in the first half of the frame and another CIRC code is used to error-correct the six multiplexed samples in the second half of the frame. A block of audio data is formed of ninety-eight such frames.
The one byte of sync control data C in each frame is thought of as containing bits P, Q, R, S, T, U, V and W; and these bits also are known as channels. Bit, or channel, Q is used in frame 1 and frame 2 of a block to indicate the beginning of that block: that is, to indicate that this is a new block of information. At present, the remaining bits, or channels, other than bit or channel Q, in the sync control data C are not used for any other purpose.
Heretofore, there has been no commercial effort to include in a block of audio data stored on a recording disc information representing text symbols which, when reproduced from the disc along with the audio information can be displayed.